Sub main earthing/CPC

[MikeAnders]

Hi all,

Trying to get my head around an external install to a garden shed.

I've run a 4mm H07 cable for the distribution circuit radial from the house. The 4mm is appropriate for VD over the distance. The cable is protected by RCD at the main consumer unit and a 20A MCB and travels up the garden clipped to a concrete wall. Then into the shed.

If I install a consumer unit in the shed, do I need to run a seperate earth cable as well? My head is saying no, its no different to running a radial, yet I keep thinking, consumer unit, seperate earth?

The installation is TN-C-S PME

The CU in the shed will be populated as:

100A Main Switch
16A MCB, 2.5mm T&E for socket radial
6A MCB, 1.5mm lighting circuit

Can someone explain why I'm getting confused?

Mikey

 

[westward10]

Assuming there is no main protective bonding in the shed another separate cpc is not required.

 

[davesparks]

If there are no extraneous parts in the outbuilding then you are unlikely to need any additional protective conductors.

Why are you fitting a CU in the outbuilding? The 16A MCB is completely pointless when it is fed by a 20A MCB

 

[telectrix]

as dave's post. why not feed the 4mm direct into socket/s and add a SFCU (5A) for lights?

 

[buzzlightyear]

https://www.electriciansforums.net/attachments/garage-shed-supplies-pdf.3514/ their you go .

 

[Zerax]

https://www.electriciansforums.net/attachments/garage-shed-supplies-pdf.3514/ their you go .

Is John Ware aka JW the Youtube chap ??

 

[Lister1987]

Is John Ware aka JW the Youtube chap ??

It is indeed John Ward, along with his YouTube channel and Flameport website with useful info on heating system types